Transdermal delivery systems are topically administered medicaments in the form of patches that deliver drugs for systemic effects at a predetermined and controlled rate. • Transdermal Drug Delivery System (TDDS) are defined as self-contained, discrete dosage forms which are also known as “patches”, when patches are applied to the intact skin, deliver the drug through the skin at a controlled rate to the systemic circulation. • TDDS are dosage forms designed to deliver a therapeutically effective amount of drug across a patient’s skin. • Currently transdermal delivery is one of the most promising methods for drug application. It reduces the load that the oral route commonly places on the digestive tract and liver. • Transdermal delivery not only provides controlled, constant administration of drugs, but also allows continuous input of drugs with short biological half-lives and eliminates pulsed entry into systemic circulation, which often causes undesirable side effects. • A transdermal drug delivery device, which may be of an active or a passive design, is a device which provides an alternative route for administering medication. These devices allow for pharmaceuticals to be delivered across the skin barrier. • A drug is applied in a relatively high dosage to the inside of a patch, which is worn on the skin for an extended period of time. Through a diffusion process, the drug enters the bloodstream directly through the skin.

1. Transdermal Drug
Delivery Systems
PRESENTED BY
SAGAR KUNDLAS
B. PHARMACY ( 8TH SEMESTER)
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2. MAHARAJA AGRASEN UNIVERSITY
(SCHOOL OF PHARMACY)
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3. INTRODUCTION
 Transdermal delivery systems are topically administered medicaments in the
form of patches that deliver drugs for systemic effects at a predetermined and
controlled rate.
 Transdermal Drug Delivery System (TDDS) are defined as self-contained,
discrete dosage forms which are also known as “patches”, when patches are
applied to the intact skin, deliver the drug through the skin at a controlled rate
to the systemic circulation.
 TDDS are dosage forms designed to deliver a therapeutically effective amount
of drug across a patient’s skin.
 Currently transdermal delivery is one of the most promising methods for drug
application. It reduces the load that the oral route commonly places on the
digestive tract and liver.
 Transdermal delivery not only provides controlled, constant administration of
drugs, but also allows continuous input of drugs with short biological half-lives
and eliminates pulsed entry into systemic circulation, which often causes
undesirable side effects.
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4. Advantages of TDD:
 As a substitute for the oral route.
 Transdermal drug delivery enables the avoidance of gastrointestinal
absorption, with its associated pitfalls of enzymatic and pH associated
deactivation.
 Rapid notification of medication in the event of emergency, as well as the
capacity to terminate drug effects rapidly via patch removal.
 Non-invasive, avoiding the inconvenience of parenteral therapy.
 The patch also permits constant dosing rather than the peaks and valleys
in medication level associated with orally administered medications. Multi-
day therapy with a single application.
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5. Disadvantages of TDDS:
 The drug that requires high blood levels cannot be administered and may
even cause irritation or sensitization of the skin.
 The adhesives may not adhere well to all types of skin and may be
uncomfortable to wear.
 High cost of the product is also a major drawback for the wide acceptance
of this product.
 Some drugs e.g. scopolamine transdermal patch placed behind the ear, it
is uncomfortable.
 Long-time adhere is difficult.
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6. Properties that influence Transdermal
Delivery:
 Release of the medicament from the vehicle.
 Penetration through the skin barrier.
 Activation of the pharmacological response.
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7. SKIN (THE LARGEST ORGAN)
 The skin is the largest organ of the human body which covers a surface area of
approximately 2 m2 and receives about one third of the blood circulation
through the body. It serves as a permeability barrier against the transdermal
absorption of various chemical and biological agents. It is one of the most
readily available organs of the body with a thickness of few millimetres which,
1. Separates the underlying blood circulation network from the outside
environment
2. Serves as a barrier against physical, chemical and microbiological attacks.
3. Acts as a thermostat in maintaining body temperature.
4. Plays role in the regulation of blood pressure.
5. Protects against the penetration of UV rays.
6. Skin is a major factor in determining the various drug delivery aspects like
permeation and absorption of drug across the dermis.
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8. Anatomy of Skin:
 The structure of human skin can be categorized into three distinct but
mutually dependent tissues:
1. The stratified, a vascular, cellular epidermis.
2. Underlying dermis of connective tissues.
3. Hypodermis.
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9. Contd.
 The Epidermis:
1. The epidermis is a continually self-renewing, stratified squamous
epithelium covering the entire outer surface of the body and primarily
composed of two parts: the living or viable cells of the Malpighian layer
(viable epidermis) and the dead cells of the stratum corneum commonly
referred to as the horny layer. Viable epidermis is further classified into
four distinct layers as shown in fig.
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10. Contd.
 The Dermis:
 Dermis is the layer of skin just beneath the epidermis which is 3 to 5 mm thick
layer and is composed of a matrix of connective tissues, which contains blood
vessels, lymph vessels, and nerves. The cutaneous blood supply has essential
function in regulation of body temperature. In terms of transdermal drug
delivery, this layer is often viewed as essentially gelled water, and thus provides
a minimal barrier to the delivery of most polar drugs, although the dermal
barrier may be significant when delivering highly lipophilic molecules.
 Hypodermis:
 The hypodermis or subcutaneous fat tissue supports the dermis and epidermis.
It serves as a fat storage area. This layer helps to regulate temperature,
provides nutritional support and mechanical protection. For transdermal drug
delivery, drug has to penetrate through all three layers and reach in systemic
circulation.
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11. RATIONALE FOR TRANSDERMAL
DRUG DELIVERY:
 Given that the skin offers such an excellent barrier to molecular transport,
the rationale for this delivery strategy needs to be carefully identified.
Clearly, there are several instances in which the most convenient of drug
intake methods (the oral route) is not feasible and when alternative routes
must be sought. Although intravenous introduction of the medicament
avoids many of these shortfalls (such as gastrointestinal and hepatic
metabolism).
 The transdermal mode offers several distinct advantages: (1) the skin
presents a relatively large and readily accessible surface area (1–2 m2) for
absorption; and (2) the application of a patch-like device to the skin
surface is a non-invasive (and thus a patient compliant) procedure that
allows continuous intervention (i.e., system repositioning, removal or
replacement).
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12. Contd.
 These include the potential for sustained release (useful for drugs with short biological
half-lives requiring frequent oral or parenteral administration) and controlled input
kinetics, which are particularly indispensable for drugs with narrow therapeutic indices.
 The implementation of TDD technology must be therapeutically “justified”: drugs with
high oral bioavailability and infrequent dosing regimens that are well accepted by
patients do not warrant such measures.
 Similarly, transdermal administration is not a means to achieve rapid bolus-type drug
inputs; rather, it is usually designed to offer slow, sustained drug delivery over
substantial periods of time and, as such, tolerance-inducing drugs or those (e.g.,
hormones) requiring chronopharmacological management are, at least to date, not
suitable.
 The excellent diffusional resistance offered by the membrane means that the daily drug
dose that can be systemically delivered through a reasonable “patch-sized” area remains
in the 10 mg range.
 This limitation imposes the first criterion for a successful transdermal candidate:
transdermal drugs must be pharmacologically potent, requiring therapeutic blood
concentrations in the ng/ml range, or less.
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